Businesses and individuals increasingly rely on computer networks for communications. For example, home users expect to receive television programming on-demand over digital networks. Businesses may rely on applications (e.g., database applications, mail server applications, word processing applications, etc.) provided over a network, such as the public Internet or a leased private network. As time passes, communication networks are expected to carry more data over some of the same communication paths in a more reliable manner. Increasingly the data paths are optical data paths, and the providers of the optical networks need to test these paths.